1. Field of the Invention
The present invention relates generally to disk drives and, more specifically, to a pivot bearing assembly having an elastomeric interface for providing vibration isolation and reducing acoustic noise levels emanating from a disk drive.
2. Description of the Related Art
Contemporary mass-produced hard disk drives employ rotary actuator structure to position transducer heads relative to recording surfaces of the disks. The rotary actuator structure includes stationary structure including a magnet assembly and rotatable structure including a pivot bearing assembly and a head stack assembly that is rotatable relative to an axis defined by the pivot bearing assembly. The head stack assembly typically comprises a body portion, a voice coil motor portion, and a set of head gimbal assemblies each carrying a transducer head for reading and writing on a magnetic disk surface.
The pivot bearing assembly typically includes a shaft and ball bearings mounted on the shaft, preloaded to reduce axial and radial play. The preload force level together with the bearings inner and outer raceway curvature, ball geometry, and fabrication materials determine the resultant axial and radial stiffness of the pivot bearing assembly. The mass and moment of inertia of the rotating parts of the pivot bearing assembly and the head stack assembly together with the pivot stiffnesses determine the frequencies of key mechanical resonant modes.
The response of the actuator structure to vibratory input is a critical element of disk drive design. Vibration can be initiated from the actuator motor as well as the motor driven spindle. Contemporary demands on disk drive performance dictate that the actuator structure have relatively low mass so as to minimize seek response time. The transducer heads must be precisely positioned by the drive's head-positioning servo system in order to read and write data recorded on the disk surface. The precision of this positioning is adversely impacted by vibration from any source, exacerbated still further by the low mass requirements. A corollary effect of the vibration is acoustic noise. The user's perception of disk drive quality may be negatively impacted by audible noise.
In prior art efforts to provide isolation of the actuator structure from induced vibration, separate damping elements have been assembled with the actuator structure attempting to provide spot damping and otherwise modify vibration response. These separate elements represent additional parts and labor, negatively impacting cost in a fiercely cost competitive product, and providing sub-optimal reduction in vibration.
Therefore, there is a need for an integrated pivot assembly which can provide damping of attached moving components from vibratory inputs to yield a disk drive which has reduced vibration with corresponding improved data transfer reliability and reduced acoustic noise.